1- INTRODUCTION

Environmental monitoring is performed to gather information about the environmental conditions and current and future trends of environment. Biomarkers have been used successfully in monitoring and evaluating the environment around the world to determine the availability and effects of chemicals.

In a report on biomarker expertise in assessing environmental hazards by the WHO, it was stated that the true definition of biomarkers includes,

“Almost any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical or biological. This quantified response can be a functional, physiological, or biochemical at the cellular level or a molecular interaction.”

The use of biomarkers has its roots in human toxins where they have been shown to be as effective as chemical exposure measures and to provide early warning signs for certain diseases. Biomarkers can be considered as a shortcut in terms of the process itself, rather than monitoring all chemicals that have a specific mechanism of action. Biomarkers are also used as early warning systems that signify potentially dangerous situations. Preferably, a biological response should occur in the space between positive conditions (beginning of anthropic event) and the onset of fatal conditions of the target body.

Biomarkers were given scores for environmental monitoring in five structures that are considered important. Those were specific for chemistry, environmental suitability, the ability to provide early warning, the ability to detect various types of chemicals and compounds, the current state of environmental monitoring, and the possibility of analysis.

2- CLASSIFICATION OF BIOMARKERS

Biomarkers are classified into three categories on the basis of their exposure in environmental assessment:

• Biomarkers of Effect
• Biomarkers of Exposure
• Biomarkers of Susceptibility

2.1-     Biomarker of Effect

Biomarkers of effect are the quantifiable changes that an individual endures which indicates an exposure to a compound and may indicate a resulting health effect.

These allow a scientist to work backwards to determine if and what kind of exposure took place, but may be too late to change anything. However, these are useful for future studies on the chemicals of interest and the results may aid in stricter laws or guidelines regarding the chemicals.

For example: After exposure to DDT, an organochloride insecticide known to cause problems in the reproductive system, a woman may experience miscarriages, which can be linked to her previous exposure.

2.2-     Biomarkers of Exposure

Biomarkers of exposure are the actual chemicals, or chemical metabolites, that can be measured in the body or after excretion from the body to determine different characteristics of an organism’s exposure.

Biomarkers of exposure are the most widely used because they can provide information on the route, pathway, and sometimes, even the source of exposure. These indicators also allow researchers to work forward in time to determine an exposure, and prevent it from causing further damage.

For example: A person or fish’s blood can be tested to see the levels of lead and therefore determine the exposure.

2.3-     Biomarkers of Susceptibility

Biomarkers of susceptibility are indicators of the natural characteristics of an organism that make it more susceptible to the effects of an exposure to a chemical.

They can help define what sensitivities are more susceptible as well as critical times when exposures can be most detrimental.

For example: The exhalation strength of an asthmatic will indicate how susceptible that person would be to the respiratory effects of exposure to brevotoxin, the toxic compound produced during a red tide.

3- IMPORTANCE OF BIOMARKERS

Different biomarkers are used for different purposes and that they all have different strength and weakness. Importance of biomarkers is

1. Biomarkers can provide precious predictive tools in bio-monitoring and ecological risk assessment around the world to detect exposure and effects of chemicals.
2. The major benefit of biomarkers is that the ecological relevance is high, which also mean that relevance for environmental management is high.
3. Biomarkers also provide significant early warning signals for specific diseases.
4. Biomarkers have also been substantial in several research projects where the aim has been to inspect the presence of pollutants and chemicals in the environment.
5. Antioxidant biomarkers are very good for early warning signs as measurable effects occur before health is impaired.

It is therefore enormously vital to use biomarkers towards the prevention events that are injurious for both man and environment. Biomarkers are also very valuable in the bioremediation or environmental renewal. Biomarkers are highly sensitive, inexpensive and easy to use.

4- SCOPE

We are passing through critical environmental changes and human beings are exposed to a number of chemicals which are directly or indirectly affecting their health and which may lead to mortality.

To escape the uncontrollable effect of environmental changes we use Biomarkers as early warning before the change in environmental parameters gets disastrous, which makes government enable to take initial effective measures as well as it helps in future planning and policy building. Biomarkers are also useful for clinical purposes. They help to foresee occurrence of disease in early stages hence early avail oneself of remedial measures. Biomarkers alert us on any abnormality in environment, it monitor problems at lowest level.

4.1-Use of Biomarkers in Aquatic Pollution Monitoring

Complex mixtures of chemical contaminant are great risk to organism in polluted environment. Anthropogenic contaminants in natural water system have potential to affect Aqua ecosystem health. These Environmental Contaminants affect the survival of aquatic organism .To predict ecosystem health and function ,Environmental Toxicologist are borrowing biomarkers from the field of medicine .Biomarkers approach are not new ,several biomarkers being used for decades. Biomarker responses can be measured in organism in order to find the effect of chemical and non chemical stressor which reduces the need for complex laboratory exposure scenario.

4.1.1-Biomarkers used to Monitor Aquatic Pollution

1. Bile Facs(Fluoresents aromatic compound)

Metabolities of Polycyclic aromatic hydrocorbon measured in bile of fish which can reflect exposure to oil.

• Metallothioneins

These are metal binding proteins that are induced on exposure to certain metals( cd , hg ). 3- PAH (Polycyclic AronaticHydrocorbon)

These Are metabolites excreted in bile of fish which can track temporal and spatial effects of oil pollution.

• Acetylcholineestrace

It is used as Biomarker for exposure as well as effect of carbamate and orgaphosphorus pesticide in both fish and invertebrate which results in decrease swimming stamina and survival.

• Heat-shock Protein

These Proteins are induced in tissues of aquatic organism in order to get response to stress including to exposure, hypoxia and temperature.

4.2-Other Uses of Biomarker

1. Research uses
2. Clinical uses
3. Public health uses
4. Policy uses

5- COMPARISON BETWEEN BIOAMARKERS AND BIOINDICATORS

Sr. No	Biomarker	Bioindicator
1.	Biomarker has been defined as a xenobiotically induced variation in cellular or biochemical processes, structures, functions that is measureable in a biological system.	Bioindicators are defined as species or group of species that readily reflects that abiotic or biotic state of an environment represents the impacts of environment.
2.	Biomarker were originally developed in the medical and veterinarian sciences. Biomarker are used at different level of organization, from subcellular to whole organisms and ecosystem and ecosystem. To identifying and understanding toxic effects initiated at sub-organisms                level(molecular, biochemical or physiology changes) and towards developing biomarkers at this level to be incorporated into routine biomonitoring programs.	Bioindicators are used in three situations Where the indicated environmental factor cannot be measuredWhere the indicated factor is difficult to measure e.g pesticides and their residues or complex toxic affluentWhere the environmental factor is easily measured but difficult to interpret e.g whether the observed changes have ecological significance.

3.	Biomarker can be considered as a shortcut where the mode of action is itself is monitored rather than all the chemicals but that have particular mode of action. For example The biomarker EROD provide information about the exposure to dioxins, planner PCBs chemical with similar structures.	Bioindicators are organisms that indicate the long-term interaction of several environmental conditions but also react to a sudden change of factors.
4.	Biomarker concepts are related to bioindicator but there is a critical difference between that, biomarker concentrate on measurement attributes. Example: The determination of sentinels on the term “predictive”. Prediction is based on correlation alone, sentinels are biomarkers and not useful for their intended purposes.	Bioindicators are also same as biomarker but the fundamental difference is that bioindicator require validation in addition to measurement. As a result of validation requirement, bioindicator are more useful than biomarker. Example: The determination of sentinels are based on prediction that is on validated knowledge of functional relationship or at least a validated corelation than sentinels are bioindicator and have some potential use in ecological risk assessment.
5.	Biomarker response should be sensitive to pollutant exposure or effects in order to serve as an early warning.	Bioindicator provide quantitative information on the quality of environment. It indicates the presence of pollutant and provide additional information about the intensity of exposure.

6- ENVIRONMENTAL MONITORING WITH BIOMARKERS IN FOREIGN COUNTRIES

Biomarkers are used in many national and regional surveillance systems around the world. Biomarkers have also been used in many research projects aimed at investigating the presence of pollutants in the environment. Below are examples of environmental monitoring programs involving biomarkers.

6.1- Sweden

Since 1988 biomarkers have been used in Sweden to monitor coastal fish. The program consists of four coastal areas of Sweden as well as two species of perch (Percafluviatilis) and eelpout (Zoarces viviparous). All sites represent background levels of pollution. Imposex in netted dog whelk (Hinianitida) is used as a biomarker for exposure to study TBT (tri-n-butyl tin) in coastal waters in Sweden. This monitoring program is used in areas where TBT levels are expected to be high, such as marinas.

6.2- United Kingdom

The UK Clean Seas Environment Monitoring Program (CSEMP) operates a network of sites where multiple maritime agencies operate on the same set of biomarkers using agreements and agreed standards. EROD, PAH metabolites in bile and DNA adducts are detected in fish to study exposure and effects of PAHs and other pollutants. These biomarkers are used in integrated experiments with concentrations of sediment and biota, as well as biological responses at high organizational levels (e.g. quantity). Imposex and intersex are used as biomarkers for exposure and effects of TBT and other contaminants in UK coastal waters.

6.3-Canada

In Canada, the pulp and paper and mining industries are being asked to provide information to assess their impact on the aquatic environment. Canada now has guidelines on how to do surveillance. Monitoring includes survival, growth, reproduction and status of the fish in the recipient. The standard design for adult fish testing recommends the collection of adult males and females of two types of species to determine whether there is a change in outcome indicators between exposure and target areas, or on the contaminant gradient.

7- CONCLUSION

An extensive variety of organisms in the environment are exposed to complex and changing levels of pollutants and their mixtures. Conventionally, the basic approach of hazard assessment was to measure the amount of chemicals present in the environment (surrounding waters, sediments, or biota), and then to relate that, via animal experimental data, to the adverse effects caused by that amount of chemical. A current approach in ecotoxicology is to examine exposed individuals for molecular and biochemical responses that are evoked by toxicants, in an effort to assess the status of an impacted environment. The primary role of biomarkers in environmental evaluation is to decide if, in a specific environment, living beings are physiologically normal. The use of biomonitoring methods in the control strategies for chemical pollution has several advantages over chemical monitoring yet it is most probable that biological-effect analysis will never totally replace chemical analyses. The biomarker approach, ought not be considered as a substitution for conventional assessment methods, but as a significant beneficial methodology of incredible ecological relevance.

Also read: SUSTAINABLE AGRICULTURE